Please tell me if this idea has already been done. I am not quite sure if I should add more information (on unusual behaviour patterns perhaps) or if I should keep it shorter. Critique is highly appreciated.

Containment procedures have been altered after previous containment breach.

I feel this isn't really needed.

through it's airlock.

Its*

currently located in the spinal region of a male human host.

Then it's not widespread nor currently extremely difficult to contain and therefore should not be classified as Keter.

Discovery of the object shouldn't be in the first paragraph. Sometimes, it's also better to leave out the discovery entirely.

We have cameras and D-Class personnel for this.

The specimen has

Why not just say SCP-XXXX?

manipulate it’s host

Its*

life forms

Lifeforms*

through combination of [DATA LOST] and an unidentifiable [DATA LOST].

Is the missing data here due to an actual system error, or is it because you couldn't come up with anything? If it's the first, I'd suggest expanding on why they haven't yet fixed the error. If it is the second, I'd try a brainstorming session to add more content to the skip.

Attempts of seperating SCP-XXXX from the host body are complicated by the nature of containment. The specimen shows extreme desire to preserve vital functions of and connection to it‘s host.

This can be left out.

Testing on live subjecs resulted in a containment breach on ██/██/200█ in which multiple staff members were manipulated into destroying vital research data on [DATA LOST], [DATA LOST] as well as [DATA LOST].

This should be in an addendum. Also, I understand now that it wants its data deleted, but how was the data deleted again after the addition was already written following the incident?

Containment was reeastablished after termination of all facility personel and flooding of the facility, forcing the specimen to return into it’s sealed chamber to avoid host death.

This seems over-the-top. Was it really necessary for all facility personnel to be terminated? I would say that it would make sense if all personnel were infected, but I really don't think the Foundation is that incompetent given that it's only a certain radius and not something like spreading as a pathogen.

Previous test subjects reported strong headache, followed by signs of dissociative identity disorder and attempts to breach containment. A list of live subject test results can be found under addendum SCP-XXXX A. Attempts of conversation with SCP-XXXX were made during these tests. A full conversation log can be found under addendum SCP-XXXX B.

I don't understand the point of this paragraph. I thought that SCP-XXXX couldn't be removed from its original host? If that's still true, then how are their previous test subjects that remain alive?

Due to the repeated attempts to breach containment, SCP-XXXX has been reassigned from object class Euclid to Keter.

Also belongs in the addenda. This is an arguable factor as to why to change its object class; purely trying to breach shouldn't do much. For example, SCP-1370 is constantly trying to breach, yet he is classified as safe. It seems that for as long as it's locked up and kept away, it can't breach. Despite this, it shouldn't be classified as safe either because it's sapient and has the ability to harm.

Addendum SCP-XXXX A:

All of this doesn't add to anything, as everything here was already stated in the description.

Addendum SCP-XXXX B:

This addendum makes the researcher in question seem ignorant because they are using a live subject rather than say, intercom systems or operated devices to speak to it.

Overall, the concept doesn't present anything new; it's a parasite that is locked up but doesn't want to be. It seems to be a combination of multiple other parasitic/disease-oriented skips but not executed as well nor as in-depth.

I personally cannot get my interest piqued by anything in this article. I would suggest adding additional anomalous properties or better addenda to enhance the article if you wish to still work with your concept.